Phenol and methyl ethyl ketone are important products in the chemical industry. For example, phenol is useful in the production of phenolic resins, bisphenol A, ε-caprolactam, adipic acid, alkyl phenols, and plasticizers, whereas methyl ethyl ketone can be used as a lacquer, a solvent and for dewaxing of lubricating oils.
The most common route for the production of methyl ethyl ketone is by dehydrogenation of sec-butyl alcohol (SBA), with the alcohol being produced by the acid-catalyzed hydration of butenes. For example, commercial scale SBA manufacture by reaction of butylene with sulfuric acid has been accomplished for many years via gas/liquid extraction.
Currently, the most common route for the production of phenol is the Hock process. This is a three-step process in which the first step involves alkylation of benzene with propylene to produce cumene, followed by oxidation of the cumene to the corresponding hydroperoxide and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. However, the world demand for phenol is growing more rapidly than that for acetone. In addition, the cost of propylene relative to that for butenes is likely to increase, due to a developing shortage of propylene. Thus, a process that uses butenes instead of propylene as feed and co-produces methyl ethyl ketone rather than acetone may be an attractive alternative route to the production of phenol.
It is known that phenol and methyl ethyl ketone can be co-produced by a variation of the Hock process in which sec-butylbenzene is oxidized to obtain sec-butylbenzene hydroperoxide and the peroxide decomposed to the desired phenol and methyl ethyl ketone. An overview of such a process is described in pages 113-122 and 261-263 of Process Economics Report No. 22B entitled “Phenol”, published by the Stanford Research Institute in December 1977.
It is also known that a mixture of phenol with varying quantities of methyl ethyl ketone and acetone can be produced by oxidizing a feed containing cumene and sec-butylbenzene and then cleaving the resultant hydroperoxides. By controlling the weight ratio of cumene to sec-butylbenzene in the feed, the ratio of acetone to methyl ethyl ketone in the product can be varied depending on market conditions. See European Published Application No. 1,088,809 and U.S. Pat. No. 7,282,613.
However, the production of phenol using sec-butylbenzene as one or the alkylbenzene precursor is accompanied by certain problems which either are not present or are less severe with a cumene-based process. For example, in comparison to cumene, oxidation of sec-butylbenzene to the corresponding hydroperoxide is very slow in the absence of a catalyst and is very sensitive to the presence of impurities. Moreover, in cumene oxidation, the major by-product is dimethyl benzyl alcohol, which is readily dehydrated to alpha-methyl styrene and hydrogenated back to cumene for recycle to the process. However, in the case of sec-butylbenzene oxidation, it is found that a significant by-product is acetophenone even when the oxidation is conducted in the presence of a catalyst, such as N-hydroxyphthalimide. Since the market for acetophenone is limited, its production could adversely impact process economics. The present disclosure seeks to address this problem by providing an integrated process for producing phenol and methyl ethyl ketone, either alone or in combination with acetone, in which the by-product acetophenone is converted to higher value products.